1. Field of the Invention
The present invention relates to an improved method for the soldering of metal parts, as well as to a device and to a filler metal for the application of said method.
It is directed more particularly to the soldering of parts, notably of aluminum tubes, and it has a very special advantage for the construction of heat exchangers.
2. Description of the Prior Art
The soldering of aluminum without flux, is at present carried out mostly by immersion of the part to be soldered in a bath of liquid filler metal and by vibrating the bath. This vibration is generally done by means of sonotrodes (heads) connected to a generator of ultrasonic energy and fixed to the outside of the tank containing the filler metal. Such a technique is notably described in U.S. Pat. No. 3,680,200.
These conventional soldering methods have a certain number of drawbacks well-known to technicians. These drawbacks, due principally to a lack of homogeneity of the ultrasonic field are manifested generally by a lack of wettability causing local filler metal defects inside the weld which weakens the latter so as to render it defective.
In addition, notably in the case of soldering of aluminum, the filler metal generally used is an alloy of zinc and of aluminum and of beryllium, as in French Pat. No. 73-29 383, or alloys of aluminum and yttrium, germanium, indium, silver, as in French Pat. No. 73-35 575, or other conventional alloys used for the soldering or welding of the aluminum.
Generally, the object sought is to avoid any soiling of the soldered area, and any troublesome overheating of the parts to be soldered and of the equipment used.
The important feature is the wetting of the metal of the part to be soldered by the molten filler metal.
It has appeared that it is more important according to the present invention that the ultrasonic energy be applied to the parts to be soldered rather than to the soldering bath, since thus the ultrasonic energy is concentrated where it is most useful, that is to say at the locus of the soldering.
It is an object of the invention to overcome the faults and drawbacks of conventional methods.
It is another object of the invention to overcome the faults and drawbacks of conventional devices.
It is yet another object of the invention to overcome the faults and drawbacks of conventional filler metals.
Other objects and advantages of the invention will emerge from the description which follows.